Silicon nanoparticles generated by femtosecond laser ablation in a liquid environment

Silicon nanoparticles were generated by femtosecond laser (387 nm, 180 fs, 1 kHz, pulse energy = 3.5 lJ (fluence = 0.8 J/cm 2 )) ablation of silicon in deionized water. Nanoparticles with dia- meters from * 5u p to*200 nm were observed to be formed in the colloidal solution. Their size distribu- tion follows log-normal function with statistical median diameter of &20 nm. Longer ablation time leads to a narrowing of the nanoparticle size distri- bution due to the interaction of the ablating laser beam with the produced nanoparticles. Raman spec- troscopy measurements confirm that the nanoparticles exhibit phonon quantum confinement effects and indicate that under the present conditions of ablation they are partially amorphous.